On a transaction fee basis.
Currently the cost of the network is roughly $300 million annually. The users of the network are collectively purchasing $300 mil worth of security each year.  If users paid $400 million the network would be more secure and if they paid $200 million it would be less secure. Today the majority of this cost is paid indirectly (or subsidized) through the creation of new coins but it is important to keep in mind the total unsubsidized security cost.  At 2 tps the network the unsubsidized cost per transaction would be about $5. At 100 tps it would be $0.05.  If Bitcoin was widely adopted, more users purchasing more coins should mean a higher exchange rate and thus the value of potential attacks also rises.  The future cost of the network will need to rise to ensure that attacks are not economical and non-economic attacks are prohibitively expense relative to the benefit for the attacker.   It may not rise linearly but it will need to rise.   If someday one Bitcoin is worth $10,000 and we are still only spending $300 million a year on security we probably are going to have a problem.  Now advocates of keeping the limit may argue that the majority of the network cost won't be paid by fees for many years but the reality is that with the limit on potential transactions there are only two other ways to balance the equation and that is much higher fees or much lower security.